The invention relates to a method for producing a windshield wiper bracket of U-shaped cross section, with two through holes disposed in the legs of the bracket, through which a rivet extends.
The invention also relates to an apparatus for producing windshield wiper bracket of U-shaped cross section, where the apparatus includes folding means for producing a U-shaped profile from a flat bracket blank provided with two through holes, a positioning mechanism for sliding a rivet slug into the through holes, which are aligned with each other after production of the U-shaped profile, and deformation means for producing at least one rivet head on the rivet slug, according to the preamble to claim 8.
Methods for producing a windshield wiper bracket of U-shaped cross section are known. With these known methods, a U-shaped bracket, whose two legs are provided with through holes that are aligned with each other, is formed in a first station. In a second station, a rivet slug is inserted through the two mutually aligned through holes in the U-shaped bracket in such a way that a free end of the rivet slug protrudes out from the corresponding through hole of the bracket. Then in a separate work cycle, the respective end of the rivet slug is wobbled to form a rivet head. This method for producing a U-shaped bracket with a rivet is relatively complex and time-consuming.
It is also known to provide a bracket, which is U-shaped and suitably embodied, with a roll rivet. In order to produce a roll rivet, the legs of the U-shaped bracket are disadvantageously weakened by means of suitable excisions so that an undesirable fracture of the roll rivet connection on the bracket can occur during operation of the windshield wiper. The roll rivet breaking off from the bracket like this can, for example, be caused by an occurrence of material fatigue. This known method for producing a U-shaped bracket while forming a roll rivet is also disadvantageously complex and time-consuming.
The method according to the invention includes the following steps:
production of through holes in a flat bracket blank;
insertion of a rivet slug into one of the through holes;
folding of the legs to produce the U-shaped profile and to thereby position of the rivet slug in a position aligned with the other through hole;
sliding of the rivet slug into the position extending through both of the through holes, and
riveting of the rivet slug.
By inserting a rivet slug into one of the two through holes of a flat bracket blank before the folding of the legs, it is possible to bring the rivet slug into the desired position aligned with regard to the two through holes while simultaneously producing the bracket with the U-shaped cross section. It is also possible to execute the sliding of the rivet slug into the position that extends through both through holes, together with the folding of the legs and the positioning of the rivet slug in one continuous work step by means of a single, suitably embodied tool. The production of a bracket with a U-shaped cross section while forming a rivet can consequently take place in a single manufacturing or processing station.
Preferably, the rivet slug is fixed in position in the bracket blank. This assures that the rivet slug is disposed in a definite position before and during the folding of the legs to produce the U-shaped profile of the bracket. Is also possible to use preassembled flat bracket blanks, each provided with the rivet slug fixed in position, in order to produce brackets with U-shaped cross sections for windshield wipers.
In order to fix it in position, the rivet slug is advantageously pressed into the through hole of the flat bracket blank, forming a press fit. A position fixing of the rivet slug in one of the two through holes of the bracket blanks by means of a press fit can be produced simply and reliably from a production engineering standpoint. The strength of the press fit between the rivet slug and bracket blank can be adapted with relative ease to each intended application, i.e. depending on the wall thickness of the bracket blank and the diameter of the rivet slug. As a result, in particular the method steps of sliding and riveting of the rivet slug can be controlled and/or adjusted in a reliable and effective manner. Furthermore, using a press fit to fix the position of the rivet slug assures that after the folding of the legs and during the sliding of the rivet slug, it aligns exactly with the other through hole and no shifting of the rivet slug in relation to the through holes occurs, which would hinder the sliding of the rivet slug.
Preferably by means of an entry bevel in operational contact with a rivet edge, the rivet slug is pushed into the other through hole of the U-shaped bracket until the rivet slug protrudes out from the through holes with its ends. Because of the definite starting position (press fit) of the rivet slug in one of the through holes of the bracket blank, it is possible after the folding of the legs, to easily and reliably slide the rivet slug out of its initial position into the end position extending through both of the through holes. In this connection, it is particularly important that the rivet slug protrudes out from the through holes in the end position so that it is possible to produce rivet heads (riveting of the rivet slug). From a production engineering standpoint, an entry bevel is relatively easy and inexpensive to produce in a corresponding manufacturing tool.
According to a preferred embodiment, the ends of the rivet slug protruding out from the U-shaped bracket are plastically deformed by means of a wobbling process to form a respective rivet head. From a process engineering standpoint, it is particularly favorable to form rivet heads on the free ends of the rivet slug protruding out from the through holes of the bracket with the U-shaped cross section, preferably simultaneously by means of a wobbling process. As a result, the bracket with the U-shaped cross section, with the rivet slug disposed in the aligned position, can maintain its original position and does not have to be brought into a special and/or new working position for the formation of the rivet heads. A wobbling process for producing a rivet head is particularly advantageous with regard to a correct and controllable material deformation on the corresponding rivet slug end. The desired and/or necessary exertion of force and consequently the material deformation for producing the rivet head can be adapted to each intended application by suitably varying the wobbling process (deformation force, adjustment angle, wobbling speed).
Advantageously, the two ends of the rivet slug are plastically deformed simultaneously. The formation of both of the ends protruding out from the through holes of the bracket into respective rivet heads permits a rapid and effective rivet production on the bracket with the U-shaped cross section.
Advantageously, the rivet slug is stabilized in its shaft part between the legs during the plastic deformation of the two ends. This effectively prevents the rivet slug from buckling during the production of the rivet heads. It is consequently easily possible to produce a correct and particularly stable rivet connection between the legs of the bracket.
According to the invention, the apparatus is characterized in that the folding means, the positioning mechanism, and the deformation means are disposed in a single processing station. The production of a bracket with a U-shaped cross section and a rivet contained in it in a single processing station is particularly favorable from a production engineering standpoint because this eliminates the transport time and/or waiting time that would otherwise occur during the manufacturing process. Furthermore, a folding of the legs, and a sliding and riveting of the rivet slug in a single processing station permits a bracket to be produced with relative ease while fulfilling particularly high precision requirements since the manufacturing tolerances in the bracket and/or the rivet, which arise due to the use of a number of processing means working in various stations, can be completely or at least partially eliminated. Furthermore, the manufacturing means used can be disposed in a single station in a particularly space-saving manner.
Advantageously, the folding means are embodied as dies which can be moved toward and away from each other in a linear fashion. Dies are tools which are particularly well suited for folding the legs to produce a profile with a U-shaped cross section since they can be produced with relative ease and can be favorably adapted to various intended applications through corresponding geometric embodiments.
The positioning mechanism is advantageously embodied as an entry bevel on one of the dies. The die provided with the entry bevel therefore simultaneously has two different operating functions, namely folding the legs to produce the U-shaped profile and sliding the rivet slug into the position extending through both through holes. From a production engineering standpoint, it is particularly easy to produce an entry bevel on one of the dies. Furthermore, an entry bevel on a die permits a relatively exact and reliable sliding of the rivet slug into the desired final position in the bracket.
Preferably, the deformation means are embodied as movable deformation elements. Movable deformation elements permit a precise deformation of the ends of the rivet slug protruding out from the through holes into respective rivet heads and this deformation can be adapted to the respective intended application.
According to a preferred embodiment, the entry bevel is embodied as a linear, straight guide edge. Using a linear, straight guide edge as the entry bevel assures a continuous sliding of the rivet slug into the position extending through both through holes. In an alternative embodiment and depending on the respective intended application, the entry bevel can also be embodied as a curved guide edge.
Preferably the deformation elements are embodied as cups which execute a wobbling motion. In this manner, it is possible for the ends of the rivet slug protruding out from the through holes to be plastically deformed into rivet heads by means of a wobbling process. In this connection, the wobbling motion of the cups, i.e. in particular the adjustment angle and the deformation force, can be adapted to the respective material and/or geometrical parameters of the rivet slug and/or the bracket with the U-shaped cross section.
The apparatus advantageously has a stabilization mechanism for the rivet part disposed between the legs of the U-shaped profile during the production of the rivet head. The stabilization mechanism prevents the rivet slug from buckling in its rivet part disposed between the legs of the U-shaped profile during the production of the rivet head due to the processing forces being exerted.
The dies are advantageously provided with a recess in the pivot region of the rivet slug. Providing a recess in the dies prevents the rivet slug that is inserted into one of the two through holes of the flat bracket blank from colliding with the die bodies during the folding of the legs to produce the U-shaped profile, since the rivet slug also necessarily executes a pivoting motion during the folding of the legs.
Preferably, the apparatus is operatively connected to a vibrator for supplying rivet slugs. Using a vibrator is a particularly reliable way to supply the apparatus with a large number of rivet slugs in succession, rapidly and in a definite position.
The apparatus advantageously has a reference element for the exact positioning of the flat bracket blank between the dies. In order to obtain a precise alignment of the two through holes after the production of the U-shaped profile, the flat bracket blank must be disposed in a correspondingly precise position with regard to the dies. In this connection, it is particularly advantageous to provide a reference element which comes into contact with a reference point or a reference line of the flat bracket blank and consequently permits an exact positioning of the flat bracket blank between the dies. A reference point or a reference line can be disposed on an edge of one of the through holes or another opening and/or edge of the flat bracket blank.
Other advantageous embodiments of the invention ensue from the description.